The present invention relates to read registers using the principle of the transfer of charges, and especially to the output circuits of such registers.
CCD-type charge transfer type read registers are used, for example, in photosensitive devices enabling the conversion of a light image into electrical charges.
The output circuit of a read register enables the conversion, into electrical signals, of the charges transferred. It is constituted by a read diode and a read amplifier.
The applications requiring the removal of the charges at a high rate lead to increasing the number of outputs for one and the same register. As is known to those skilled in the art, the read amplifier of each output is generally constituted by several series-connected amplification stages. The bias currents of the successive amplification stages then have increasing values. For example, a read amplifier constituted by three amplification stages may then have to give current of the order of 15 mA at a voltage of 15 volts. It is then not possible to greatly increase the number of outputs as would be desirable, for the power that would have to be dissipated by the read register would then speedily reach excessively high values. For example, a read register with 32 outputs, each having a read amplifier biased as mentioned here above (15 mA, 15 volts), cannot be made for it would result in an amount of power dissipated in the register of about 7 watts.
The invention does not have this drawback.